STRSEP(3) FreeBSD Library Functions Manual STRSEP(3)


strsepseparate strings


Standard C Library (libc, -lc)


#include < string.h>

char *
strsep( char **stringp, const char *delim);


The strsep() function locates, in the string referenced by *stringp, the first occurrence of any character in the string delim (or the terminating ‘ \0’ character) and replaces it with a ‘ \0’. The location of the next character after the delimiter character (or NULL, if the end of the string was reached) is stored in *stringp. The original value of *stringp is returned.

An “empty” field (i.e., a character in the string delim occurs as the first character of *stringp) can be detected by comparing the location referenced by the returned pointer to ‘ \0’.

If *stringp is initially NULL, strsep() returns NULL.


The following uses strsep() to parse a string, and prints each token in separate line:

char *token, *string, *tofree; 
tofree = string = strdup("abc,def,ghi"); 
assert(string != NULL); 
while ((token = strsep(&string, ",")) != NULL) 
 printf("%s\n", token); 

The following uses strsep() to parse a string, containing tokens delimited by white space, into an argument vector:

char **ap, *argv[10], *inputstring; 
for (ap = argv; (*ap = strsep(&inputstring, "\t")) != NULL;) 
 if (**ap != '\0') 
  if (++ap >= &argv[10]) 


The strsep() function is intended as a replacement for the strtok() function. While the strtok() function should be preferred for portability reasons (it conforms to ISO/IEC 9899:1990 (“ISO C90”)) it is unable to handle empty fields, i.e., detect fields delimited by two adjacent delimiter characters, or to be used for more than a single string at a time. The strsep() function first appeared in 4.4BSD.
December 5, 2008 FreeBSD